At 11th level, you gain the ability to thwart someone else's magic. When you see a creature casting a spell or teleporting within 60 feet of you, you can use your reaction to try to magically foil it. The creature must succeed on a Wisdom saving throw against your spell save DC, or its spell or teleport fails and is wasted.
Once you use this feature, you can't use it again until you finish a short or long rest.